| → instinct 1861 1866 |
| it was instinct 1869 1872 |
|
| → slightly changed; nor can we conjecture by what gradations many instincts have been developed when they relate to organs (such as the mammary glands) on the first origin of which we know nothing. 1861 1866 |
| varied. 1869 1872 |
|
| → have been independently acquired by 1866 |
| have been acquired by independent acts of 1859 1860 1861 |
| were independently acquired through 1869 1872 |
|
|
so in other cases. It
admitted that in many instances we cannot conjecture whether
→instinct
or structure
first
→slightly changed; nor can we conjecture by what gradations many instincts have been developed when they relate to organs (such as the mammary glands) on the first origin of which we know nothing.
|
|
| No doubt many instincts of very difficult explanation could be opposed to the theory of natural
cases, in which we cannot see how an instinct could
have originated; cases, in which no intermediate gradations are known to exist; cases of instinct of
such trifling importance, that they could hardly have been acted on by natural selection; cases of instincts almost identically the same in animals so remote in the scale of nature, that we cannot account for their similarity by inheritance from a common
and
believe that they
→have been independently acquired by
natural selection. I will not here enter on these several cases, but will confine myself to one special difficulty, which at first appeared to me insuperable, and actually fatal to
whole theory. I allude to the neuters or sterile females in insect-communities: for these neuters often differ widely in instinct and in structure from both the males and fertile females, and yet, from being sterile, they cannot propagate their kind. |
|
| The subject well deserves to be discussed at great length, but I will here take only a single case, that of working or sterile ants. How the workers have been rendered sterile is a difficulty; but not much greater than that of any other striking modification of structure; for it can be shown that some insects and other articulate animals in a state of nature occasionally become sterile; and if such insects had been social, and
|
